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https://issues.apache.org/jira/browse/CASSANDRA-18134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17690430#comment-17690430
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Michael Semb Wever commented on CASSANDRA-18134:
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So, for the sake of discussion: because the only precedence we have today (look
at BigFormat's history) is any format bump in a major version has always been a
major format change; if we are to bump trunk to {{\-nc\-}} the problem scenario
I raise has (at least) the four following possibility:
1. Release branches for 4.0 and 4.1 are fixed to {{\-nb\-}}. No format changes
are permitted.
2. Any eventual format change on 4.0 or 4.1 requires first back-porting (all or
some minimal support of) the {{\-nc\-}} change, with the new change happening
in {{\-nd\-}}. (Aleksey's comment directly above.)
3. Some minimal version of the {{\-nc\-}} is committed to 4.0 and 4.1 branches
now. (Aleksey's comment two above.)
4. Reserve some sequence of minor versions for 4.0 and 4.1 branches, e.g. this
change goes into trunk as {{\-nn\-}}
All of these are painful IMHO. (1) is shoots our foot off. (2) is tech debt and
introduces risk on release branches (think about needing a CVE patch quickly
and this getting in the way). It is unclear if (4) is currently possible
(though we do something similar with verbs).
I'm still in favour of this patch landing in trunk with {{\-oa\-}} as the
simplest solution. A major format change (even if superficial) aligned with a
major release is our current practice and what user's expect and know to deal
with. We can do better, and [~yukim] proposes a solution that is much aligned
with [~cscotta] in CASSANDRA-8110, but let's not block this ticket on that work.
> Improve handling of min/max clustering in sstable
> -------------------------------------------------
>
> Key: CASSANDRA-18134
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18134
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/SSTable
> Reporter: Jacek Lewandowski
> Assignee: Jacek Lewandowski
> Priority: Normal
> Fix For: 5.x
>
>
> This patch improves the following things:
> # SSTable metadata will store a covered slice in addition min/max
> clusterings. The difference is that for slices there is available the type of
> a bound rather than just a clustering. In particular it will provide the
> information whether the lower and upper bound of an sstable is opened or
> closed. The legacy min/max clustering will be stored until a new major format
> {{o}} to ensure backward compatibility
> # SSTable metadata will store a flag whether the SSTable contains any
> partition level deletions or not
> # SSTable metadata will store the first and the last keys of the sstable.
> This is mostly for consistency - key range is logically a part of stats
> metadata. So far it is stored at the end of the index summary. After this
> change, index summary will be no longer needed to read key range of an
> sstable (although we will keep storing key range as before for compatibility
> reasons)
> # The above two changes required to introduce a new minor format for SSTables
> - {{nc}}
> # Single partition read command makes use of the above changes. In particular
> an sstable can be skipped when it does not intersect with the column filter,
> does not have partition level deletions and does not have statics; In case
> there are partition level deletions, but the other conditions are satisfied,
> only the partition header needs to be accessed (tests attached)
> # Skipping sstables assuming those three conditions are satisfied has been
> implemented also for partition range queries (tests attached). Also added
> minor separate statistics to record the number of accessed sstables in
> partition reads because now not all of them need to be accessed. That
> statistics is also needed in tests to confirm skipping.
> # Artificial lower bound marker is now an object on its own and is not
> implemented as a special case of range tombstone bound. Instead it sorts
> right before the lowest available bound in the data
> # Extended the lower bound optimization usage due the 1 and 2
> # Do not initialize iterator just to get a cached partition and associated
> columns index. The purpose of using lower bound optimization was to avoid
> opening an iterator of an sstable if possible.
> See also CASSANDRA-14861
> The changes in this patch include work of [~blambov], [~slebresne],
> [~jakubzytka] and [~jlewandowski]
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